Hi Samar,
Sorry, we did not remove any fields. This was standard business content installed without making any changes or modifications to it. Our business process, as any company should be, is to never make hard changes to standard SAP content. If we wanted to add or remove fields, we would actually replicate the Query, DSO, Cube, Object, etc. as a 'Z' one. So instead of modifying 0PCCP_M10, we would have instead created an identical copy and with a technical name of ZPCCP_M10 and then built did the same for the queries and then do our custom changes. However, the error is coming from the default installation; no modifications were made.
Also, you can only remove objects from a query from display purposes. The object itself will still remain in your display on the left hand side in your query designer. As you can see from my screenshot, the error message that's being displayed says that the reference object is not in the InfoProvider. InfoProviders are your Cubes, DSOs, MultiProviders, Infosets, and Virtual Cubes. Had it been an issue with it not being displayed in the query because I accidentally removed it, it would not throw an error referencing my InfoProvider as missing it; you would actually get a different error.
Interestingly however, I created a new Z MultiProvider and REMOVED the 0LOTSIZE_CM object, and all was well. I have a question into our Finance department as to whether or not they need Lot Size on their report. If not, I'm just going to go with everything custom instead. Sad that I can't use standard SAP. And although your answer did not help Samar, I am grateful that you took a stab at it and replied. Nothing worse than a question that goes un-answered. 